well her grandma died and her only family died so I would k*ll him too if i were her
Yes but if she didn't kill him, the police could have had more information on his killings (if he indeed is the killer)and on Han Kook's whereabouts. I know she was emotional because he might have killed her grandma and hurt Bareum, but to me that was still very selfish of her. She took away the last hope of Han Kook's mother to find her son (again if yohan is really the killer). Once they would have gotten all the information from him or if he refused to cooperate, then okay, go ahead and kill him.